Vacuum furnace for heat treatment to enhance convection heat transfer
The resistance furnace used in heat treatment vacuum furnace industry is generally composed of electric heating elements, masonry, metal shell, furnace door, furnace machinery and electrical control system. The heating power ranges from less than one kilowatt to thousands of kilowatts. Working temperature below 650 ℃ low temperature furnace; 650 ~ 1000 ℃ temperature in the furnace; More than 1000 ℃ high temperature furnace. In the high and medium temperature furnace, the main heating way is radiation. In the low-temperature furnace, it is heated by means of convection heat transfer. The electric heating elements are installed in the air duct, and the gas circulation in the furnace is forced by the fan to strengthen convection heat transfer. Resistance furnace chamber type, well type, trolley type, push rod type, step type, muffle type and tunnel type. Controllable atmosphere furnace, vacuum furnace, flow particle furnace are also resistance furnace.
All the masters of the vacuum furnace know to start the vacuum furnace power supply and set the switch of the control cabinet in the position of automatic control. The parameters of the vacuum furnace process specification are input into the computer. Then the workpiece is sent to the furnace smoothly with the charging trolley, and the furnace door (cover) is closed and locked to ensure the sealing. According to the process requirements to choose a good vacuum furnace cooling medium and cooling methods and pressure. Press the circulation starting button, the equipment execution procedure: vacuum _ heating _ cooling is completed automatically. Remember to check the normal operation of all systems at any time, and report to the foreman if there is any abnormality. Before coming out of the furnace, the normal pressure in the furnace should be restored, and the door (cover) of the furnace should be opened after the indicator light is normal. Unloading, should be carefully operated, the workpiece and tooling are not collision furnace.
There are two main aspects to control the difficulty. First, how to get the carbon out of the lowest range within 15 minutes; Second, according to the 15 minutes of decarburization determined by the residual oxygen content in the steel liquid, aluminum one-time addition in place, both to ensure that aluminum deoxidation, but also to ensure that the aluminum alloy. In this way, the smelting time can be controlled in 25 to 30 minutes. Otherwise, the vacuum treatment time will be greatly extended. Smelting in the process of production of ultra-low carbon steel, as the extension of time, the contact between refractory material and steel liquid will lead to carbon steel back, in addition, the amount of ultra-low carbon steel because of the addition of aluminum is larger, a lot of Al2O3 inclusions produce, so the aluminum to join the sooner, the more conducive to Al2O3 inclusions floatation, the more conducive to the process after the operation and improve the quality of our products.